Your overclock is high and might actually be making your performance worse.
Try running it at stock settings to see if it helps. I haven't tested that yet with the drivers I'm using at the moment (not sure the driver even matters) but I've had my performance plummet when overclocking a little too far. For example, going from 470 on the core to 475 actually caused my performance to drop considerably (from like 12k in 3DMark05 to around 9K). I'm not sure if it is throttling or what when that happens. So, I suggested using stock settings to see if something similar was happening to you.

I had low 3DMArk05 scores.... at about 6500. Most forums suggest that this is due to the puny Intel 3.0ghz limitation.

SO I decided to overclock the hell out of it in hopes of saving my rig. Since I am a noob to overclocking... i had many start and stops... finally managed to get a stable clock at 3.45Ghz.... And the results were very encouraging..

New 3DMark05 score at 7498!!! Does not touch the 8k++ figures some others are putting up.... but my 7800GTX is not OCed yet... still stock at 430/1200. At least now I feel better about my rig. Game play is slightly better as frame rates have improved.

Next will have to learn up a little bit more about OCing to higher frequencies... next target 3.6Ghz!!